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Commit 3cdf6fe9 authored by Seunghun Lee's avatar Seunghun Lee Committed by Miklos Szeredi
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ovl: Prevent rw remount when it should be ro mount 



Overlayfs should be mounted read-only when upper-fs is read-only or nonexistent.
But now it can be remounted read-write and this can cause kernel panic.
So we should prevent read-write remount when the above situation happens.

Signed-off-by: default avatarSeunghun Lee <waydi1@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent a425c037

fs/overlayfs/super.c

+12 −0
Original line number Diff line number Diff line
@@ -525,10 +525,22 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry) 
	return 0;

}



static int ovl_remount(struct super_block *sb, int *flags, char *data)

{

	struct ovl_fs *ufs = sb->s_fs_info;



	if (!(*flags & MS_RDONLY) &&

	    (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)))

		return -EROFS;



	return 0;

}



static const struct super_operations ovl_super_operations = {

	.put_super	= ovl_put_super,

	.statfs		= ovl_statfs,

	.show_options	= ovl_show_options,

	.remount_fs	= ovl_remount,

};



enum {